Sir Elton John and his partner David Furnish are rumoured to be making another addition to their family.

The pair - who welcomed baby Zachary into the world in December 2010 with the help of a surrogate mum - hope to have a brother or sister for their son by the end of the year, the Daily Mirror reports.

A source told the newspaper: "The wheels are in motion. David and Elton have never hidden their desire to extend their family, and believe the time is right for another child... they are incredibly excited and loving every minute of parenthood."

Sir Elton has previously voiced concerns about Zachary facing homophobia as the son of two gay parents.

He revealed last November: "As he grows up he'll become his own man and we'll be incredibly proud of whatever choices he makes. He may one day be straight, he may one day be gay. He may turn out to be an athlete. Or a booklover. Or both. He can be whatever he likes and we'll continue to treasure him, as we do now, like nothing else in the world."

"But above all, we want him to be safe. And we're determined that he'll grow up in a world different from the world that we grew up in ourselves."

A spokesman for Sir Elton declined to comment on claims the pair were planning to have another child.